@Chimera: I know, same thing here. I know that if you create hallways without a ceiling, forget about it. I can't even get the player to take a step. I've also found that if you look down at the floor while walking, the FPS jumps way up.
Anyway, I've got a 128MB card at home and I've already ordered a new 256MB card. I'm also upgrading to 1.5MB Ram from 768. Hopefully that will be enough to make it run smoothly so I can create more complex levels.
Right now, I'm just sticking to small stuff just to learn the editor.
"Beware of people who try and belittle your ambitions. Small people do that. The really great people are the ones who make you feel that you too can become great" --Mark Twain